Keirin chains are often blowing in the wind, too. However, the consequences of an unshipped chain on a track are not as serious as when you're on the road, going downhill at 150rpm, with an impatient car driver up your arse, which is a daily occurrence for me.
As tight as possible without binding is what I aim for. The "without binding" is important. It also pays to buy decent chainrings and sprockets, and to centre the chainring on the crank properly - this enables you to get the chain tighter throughout its rotation. With cheap sprockets and chainrings, you often end up with a very slack spot just to avoid binding at the tightest spot. Bigger cogs (e.g. 48 x 18, or even 52 x 20) are more forgiving of concentricity errors than smaller ones (e.g. 42 x 16, or 39 x 14 like I used to run on an MTB conversion).
If you want real insurance (HEALTH WARNING - DO THIS VERY CAREFULLY AND USE A TOOL RATHER THAN YOUR FINGER IF YOU'RE ACCIDENT-PRONE), turn the pedals slowly when the chain is at the slackest spot and try to derail it as it feeds onto the chainring. If you can't manage this, the chain is tight enough for safety, at least until it wears a bit and gets slacker.